This invention relates to a seat of a passenger vehicle such as an automobile. In particular, this invention relates to such a seat that considers its safety when a rear impact acts thereon.
FIG. 1 shows a bucket seat typically installed in a passenger vehicle such as an automobile. The seat 10 comprises a seat part 11, a backrest 12 attached to the rear side of the seat part 11 and a headrest 13 attached to the top part of the backrest 12. The seat part 11 and the backrest 12 have cushions, respectively. The cushion of the backrest 12 supports a back of a passenger sat on the cushion of the seat part 11.
FIG. 2 shows a conventional frame structure of a seat as shown in FIG. 1. As shown, the frame structure has a bottom frame 20 as a main frame of the seat part 11 and a back frame 40 as a main frame of the backrest 12.
The bottom frame 20 has side supporting frame members 21, 22. One side supporting frame member 21 is positioned opposite to another side supporting frame member 22. Reinforcing members such as beams indicated by numerals 23, 24, 25 connect the side supporting frame members 21, 22 to reinforce the bottom frame 20.
The back frame 40 has side plates 31, 32 that are connected to rear parts of the side supporting frame members 21, 22, respectively, and top parts of these side plates 31, 32 are connected by an inverse U shaped member 34 formed of, for example, a bar or tube. Headrest attaching members 35,36 are fixed to a top part of the member 34, and the headrest 13 can be attached to the top part of the backrest 12 by passing two legs (not shown) of the headrest 13 through holes of these members 35, 36. As shown, a reinforcing member such as a plate indicated by numeral 41 connects lower parts of the side plates 31, 32 to reinforce the back frame 40.
The seat 10 as shown in FIG. 1 further comprises reclining means 42, 43 for adjusting a tilt angle of the backrest 12 with respect to the seat part 11 (see, for example, Japanese Patent Laying-Open No. 2003-52476).
If a rear impact due to an accidental collision and the like acts on an automobile that installs such a seat and then acts on a passenger sat on the seat, the passenger will be injured. If a hard impact acts thereon, a backrest of the seat will be tilted rearward and the passenger will slide up along the backrest, and as a result, the passenger will suffers a serious injury.
Recently, a seat of an automobile has been provided with a headrest as shown in FIG. 1 in order to protect a passenger from such an impact due to an accidental collision. That is, if there is no headrest, the passenger's head will be tilted (or rotated) rearward and the passenger's neck suffers a serious damage due to the rear impact. Thus, the headrest serves to protect the passenger's head and neck so that the passenger does not suffer whiplash injury due to the rear impact.
The headrest can hold the head to restrain a large rearward tilting (or rotation) of the head. However, disadvantageously, if the impact energy is larger, the backrest will be tilted rearward and the passenger will slide up such that the passenger's head rides over the headrest to injure in the passenger's neck and the passenger may be thrown out of the seat.
In addition, if the front seat is tilted rearward when a rear impact acts thereon, a rear space behind the front seat becomes smaller and a passenger sat on a rear seat will be injured.
Accordingly, in automotive industry, it is a technical problem to improve a passenger's safety when a rear impact acts on a seat.